Shock absorbers are designed to dampen relative motion between a wheel and chassis of a motor vehicle. They are often designed such that the dampening rate of the shock becomes higher at either extreme of the suspension displacement, namely rebound and jounce. A variety of mechanisms increase resistance to extreme jounce and rebound suspension movements. Rebound springs and elastomeric jounce bumpers have been used internally and externally of the working cylinder. In addition, secondary pistons have been used which become operative only at the extreme ends of the piston rod stroke.
The present invention is directed at controlling extreme rebound suspension motions. Conventional rebound control mechanisms present an undesirable ride harshness when a suspension extends into rebound limits of travel. There are two components to the undesirable harshness: switching harshness and rebound stop harshness. Switching harshness results when the shock changes over to a higher dampening rate to assist resisting the sudden impact of the suspension at the extreme suspension extension. Rebound stop harshness results when the suspension reaches its mechanical limit of travel, and the suspension components stop relative motion between the wheel and chassis. Passengers perceive these events as undesirable.
It would be desirable to provide a shock absorber capable of increasing the hydraulic resistance and a providing a hydraulic stop without undesirable switching harshness.